Traditionally, in fluid conditioning stations the pumping devices are started and stopped in such a way that the pressure in the fluid accumulating container(s) is kept between two pressure limiting values, called start pressure, which is determined in function of minimum values to be maintained, and stop pressure which is determined in function of the maximum recommendable number of starts per unit of time of the pumping devices.
Said stations presented the disadvantage of not adapting well to consumption, which is random and can vary across wide values. One example of variable consumption is to be found in hospitals, in which consumption is maximum in the mornings of working days (due to an increase in operating and resuscitation theatres in use) and minimum on Saturdays and Sundays and particularly in the month of August. The ratio between maximum consumption and minimum consumption can easily be 5 to 1.
In these cases, the starting and stopping of the pumping devices took no account at all of the possibility of adapting the station to consumption, so that, for example, a high-power pumping device could be started up for a small consumption flow.
This system involved a considerable squandering of energy and high wear of pumping devices, which resulted in shorter pump life.
Moreover, the flow supplied by the station was not suitably controlled, since the most suitable combination of pumping devices was not always in operation.
Spanish patent application P9300399 by the same applicants suggested several solutions for the aforesaid problems.
Essentially, said application is characterized in that only one pumping device is put into operation when the pressure in the fluid accumulator containers reaches or exceeds the start pressure value and/or when the flow provided by the pumping devices which are operating is lower than the consumption flow; and only one pumping device stops when the pressure in the fluid accumulator containers reaches the stop pressure value and/or when the flow provided by the pumping devices which are operating exceeds the consumption flow.
This feature allowed a stepped increase of the flow provided by the station to be ensured, in as many steps as there were pumping devices making up peak flow at the station in question, together with progressive adaptation to changing consumption.
The aforesaid patent application also suggests other possibilities for controlling stopping of the pumping devices by means of conditions such as a number of starts/stops per unit of time, or by fixing a cycle during which there can be no stoppage. Also suggested as an alternative to stopping a pumping device which can operate without pumping ("stand by").